Hollow conductor



W. H. BASSETT HOLLOW CONDUCTOR Filed Oct. 5, 1924 'Patented Aug. 24, 1926.

UNITED STATES 1,597,422 PATENT OFFICE.

WILLIAM H. BASSETT, OF CHESHIRE, CONNECTICUT, ASSIGNOR TO THE AMERICAN BRASS COMPANY, OF WATERBURY, CONNECTICUT, A CORPORATION OF CONNECTI- CUT.

HOLLOW CONDUCTOR.

Application ma October a, 1924. Serial No. 741,843.

when used to transmit high voltage alt My invention relates to hollow conductors which are of relatively large diamter for a given cross-sectional area of the conducting material so as to permit them to be used for high voltage transmission without substantial corona loss or for other purposes requiring maximum diameter and surface with re uced cross-section of-conducting material, and has for its object to produce a new and im roved hollow conductor of the required exibility, high resistance to mechanical injury liable to result from crushing stresses, high tensile strength, maximum conductin efiiciency, and relatively low weight. y improved conductor may be used bare 0r insulated as occasion requires.

Conductors heretofore made have been open to various objections. Thus, solid conductors when used for high voltage transmission are of such small diameter that the corona losses are so great as to render the transmission relatively inefiicient, a disad vantage which numerous inventors have attempted to overcome by making the conductors hollow and thus increasing the diameter of the conductors relativelyto the crosssectional area of the conducting material. Hollow conductors have been made by cabling conducting wires or strands about tubes of lead, resulting in conductors deficient in conductivity for a given weight, or lacking in tensile strength and power to resist crushing effects. It has also been roosed to cable wires or strands about a olow flexible metal tube. In such cables, however, the tube did not practically increase the conductivity of the cable or its tensile strength, or aiford the desired degree of resistance to crushing efiect or other mechanical injury. Hollow cables with internal'supporting means composed of helically wound wire have also been suggested but these are open to the same objections as nating currents. Various other forms of cable have been suggested which have presented some or all of the above disadvantages, any one of which is objectionable particularly on account of the great lengths of transmission lines used at the present time, the consequent large production necessary in order to supply the demand, and the service which a cable has to render. I

'I have discovered that if a metal strip of novel form is used instead of a plain strip thick enough to support the spiral strands without cutting, the weight of metal in the strip can be much reduced so as to effect a very considerable saving without reducing the efficiency of thecable, thus cutting down the cost of the cable itself and the cost of installing it and its supports. I hate further discovered that a metal strip of a given weight can be so formed that a cable comprising it will have greater conducting efficiency than a cable of equal diameter and weight having a plain twisted metal strip of the same weight as my strip. The saving and advantages are of importance when the total amount of metal and current carried are considered, such cables being at times hundreds of miles in length and carrying heavy currents.

' In carrying out my invention I einploy a twisted strip of a peculiar form which decreases the cost of the cable, avoids the objections of the suggested twisted strip cables above referred to, and also those of the lead tube cable and the flexible tube cable and the other cables and acts effectively to increase the conductivity of the cable particularly when carrying alternating currents. To avoid the diiliculties and secure the advantages referred to I form a twisted strip having projecting flanges at its edges so that in cross-section it is thickened at the edges and somewhat in the shape of an I-beam. I also curve the head surfaces of the I-strip so that the twisted strip will present transversely curved supporting surfaces to the inner surface of the tube formed by the cabled strands engaging therewith. These supporting surfaces are spiral and extend a considerable distance longitudinally of each strand so as to support the same without danger of cutting them at the points of en agement. The

its weight is less than if it were uniformly of a thickness equal to the width of the heads. Moreover, the thickened edges being remote from the center of the cable act to afford a conductira path at points where there is a concentration of the current due to the well known effect of alternating currents so that the conducting efiiciency for a given weight'of metal is increased.

While the twisted strip may be of the same material as the conducting wires or strands cabled about it, it may be made of other suitable metal alloy. I preferably make the conducting strands or wires of copper or copper alloy and make the twisted strip of a similar material. Such copper or copper alloys can beeti'ectively worked and provide is necessary strength and stress resisting characteristics.

in making .he hollow conductor, the conductor wire or or cabled around so as to he laid 1 may one i anus are spirally wrapped bll Lshaped twisted strip '11 s iral courses and there 0.. i ore than one. Such wires or stran may as spiralled in either direction but prefer to cable the inner layer around. direction opposite to the twist of the strip and i e succeeding layer in the same direction. as the twist of the strip.

With the construction described, ameter of the cable is large for sectional. area of conducting material and cables of very considerfible size may be formed so as to be adapted for very high voltage tran mission without suhstantial corona loss and for other purp requiring large diameter and surface .rh relatively small cross-section of conducting 111:1- terial. The major of the conduc. 1 material, inclurzz the cable wires and the flanges on the strip, is ibuted at the outer portions oi the c that, when frequencies I19. di-

fie ing my invention is shown in the accompanying drawings, in which i ure 1 "we a portion of cable partly in s a partly broken away;

rig. 2 sows a transverse section of the same on the ?.-2, F 1g. 1;

i o ea c a. portion 01 t e stiip on and 'n an enlarged scale, a strip.

particularly to the drawresents a twisted strip having laterally projecting portions. or

flanges forming thickened edges or heads 4l so as to make it substantially I-shaped in cross-section. The outer surfaces 66 of these heads are curved so as to substantially conform to the inner surfaces of wires or strands cabled thereon. The central part 8 of the body portion of the strip may be thickened so as to give the strip greater tensile strength as shown in Fig. 4. The twisted strip is twisted about its longitudinal axis, the preferable pitch being about one complete twist to four inches for a strip five-eigths of an inch in width. A strip cl such width whose body portion is .044) of an inch thick and whose edges are of an inch thick gives satisfactory results.

About the twisted strip, wires or strands 10 are cabled and if desired another layer of wires or strands 12, thus making up the completed cable as shown. As shown in the drawings the wires or strands are round but obviously that form of wire or strand is notnecessary to the embodiment or the invention.

in forming the cable the strip in un twisted form with its proje ting flanges is first produced. It is then twisted as shown and then fed to a cabling machine where it is surrounded with one or mor layers of conducting wires or strands thus producing the complete cable.

The thiczened edges of the core of especial importance in connection with the wnutacture of the cable. Ffhere fiat r.li'lD is used, the strip bein" *isted oi'tcn suddenly changes from a s", twist to a helical twist or curl which would con 'nue for a toot or more before it could be st Jed. in some cases in working with the flat trip this has happened so often to spoil the entire lot even for QXpETl' a l purposes. single spot where the twist has changed from a spiral form to a helical form ruins the core for commercial purposes. When the strip has the flanges described herein this difiiculty is eliminated, and cores many miles in length can be made without defects in the twist.

is will be evident to those s illed in the art, my invention permits of various modilications without departing from the spirit thereof or the scope of the appended claims.

l fhat I claim is 2*- 0 In a conducting cable 0" strands cabled so formed by a twist ody portion and projecting mg thickened edges thereo providing thickened condi g and spiral surfaces engaged by saith" and supporting the same.

2. In aconducting cable comprising a se ries of strands cabled so as so iorm a tube, a core formed of a twisteail crip having a body portion and progecting flanges faces supportin -vidin upon its edges so as to have an I-sha ed cross-section, said flanges providing thlckened conducting portions and spiral sursaid strands' 3. In a con ucting cable comprising a series of strands cabled so as to form a tube, a core formed by a. twisted strip having a bod portion and projecting flan es forming thiciiened edges thereon, said flanges prothickened conducting portions and spira surfaces engaged by said strands and supporting the same, said spiral surfaces being curved transversely soas to substan tially conform to the inner surface of the tube.

4. In a conducting cable com rising a series of strands cabled so as to orm a tube, a core formed b a twisted strip having a bod portion an rojecting flan es forming thic ened edges t ereon, said anges providing thickened conducting ortions and spiral surfaces engaged by sai strands and supporting the same, said thickened conducting ortions being about twice as thick as the jacent body portion.

WILLIAM H. BASSETT. 

